The regulation of cyclic nucleotide phosphodiesterase and adenylate cyclase activities by Ca2 ion will be investigated in cell free preparations of rat or beef brain and other tissues. Specific forms of each of these enzymes are deactivated by the removal on anion exchange chromatography of Ca2 ion-dependent regulator (CDR) identified previously as a heat stable, acidic Ca2 ion-binding protein which has been purified to homogeneity. These enzymes are reactivated by the readdition of CDR and Ca2 ion. Primary emphasis will be placed on dissociating the detergent dispersed CDR-dependent adenylate cyclase into its substituent components followed by recombination of the components and reactivation of the activity. The separated components will be identified, purified, and characterized. Physical relationships of the CDR-dependent adenylate cyclase with CDR-independent forms of the enzyme will be sought. Alteration of the ratio of Ca2 ion-dependent to Ca2 ion-independent cAMP accumulation in C-6 glial tumor cells will be sought with pharmacologic probes. The physiologic substrate specificity of the CDR-dependent phosphodiesterase will be studied by following cyclic nucleotide degradation in intact Ca2 ion-restored and Ca2 ion-depleted cells.